BACHMANN ANNOUNCE O4

[IAK]

As I can see it for those so inclined.
Buy one and run it in and wait for the corrective parts that will, as sure as eggs is eggs, will appear.
If like me, you have a queue of items for work bench attention, this will see an eventual outcome of a satisfying nature...

[jwealleans]

... and if, like me, you'd almost certainly repaint it anyway, wait until Hattons have surplus and start discounting the unpopular variants....

[Atlantic 3279]

Yep. I realise that if I'd waited not too long I might have got one for £20 to £30 less with relatively little difficulty - look at super D prices now, yet really cheap A1s seem not to exist.

[IAK]

... and if, like me, you'd almost certainly repaint it anyway, wait until Hattons have surplus and start discounting the unpopular variants....

Sssshhhhhhhhh quiet

[Atlantic 3279]

A couple more observations on the Bachmann O4 now I've had mine in pieces. These may help those having doubts about some of the inaccuracies.
The pony truck: Although the truck as factory fitted is a mil or so too far forward, once detached from its mount the "eye" through which the pivot screw for the truck passes is seen to be an opening in the rear of an oval patch of plastic. Bachmann appear to have catered for those who would like to blank off the existing hole and re-drill a new one further forwards in order to move the truck back to its "scale" position.

The live loco-tender drawbar: whilst this is festooned with clipped-on wires and at first glance "permanently" attached to loco and tender, things aren't as bad as they appear. The BRM review correctly pointed out that the plug for the wiring can be detached from the loco. It did not point out the following - once the screw concealed by the four wires is withdrawn from the loco end of the drawbar (which has to be done to release the rear end of the loco body from the chassis) then with body lifted it is simple to un-hook the drawbar from its loco-end pivot, uncoupling loco and tender completely. This screw must have been taken out for the BRM photos so I don't know why no more was said. Also, the yawning chasm between loco and tender can be fixed EASILY without drawbar modification or chopping out wiring between loco and tender. The tender end of the drawbar is slotted, and pivots on a screw concealed above the first axle of the tender. The gap can be shortened to virtually nil if desired! On my loco the screw was in fact done up "just nicely" to the point at which there was enough friction to maintain drawbar length under ordinary conditions, but still enough freedom to alter the length just by pushing together or pulling apart the loco and tender.

And a quick trial last night gave a very favourable impression of my chances of getting my O1 body onto the chassis, and running, pretty quickly. Alternative O4/8 boiler, cab and saddle are not far off trial-fitting condition now either.

I'm less happy about the con-rods on the O4. They are cast, giving a scale-thickness look, but when they then have to be unrealistically elbowed to clear the crankpins and joint-pins on the second coupled wheelset, what's the point to it all? I'm a bit wary of trying to straighten cast rods (possibly muck-metal). With slightly thinner con-rods and/or less protuberent "sqaure ended" pins in the coupling rods, no elbows would be needed!

[Atlantic 3279]

Here's my B1-based O1 body now adapted so as to screw securely at the the correct height and angle onto a Bachmann O4 chassis that has had no irreversible alterations. There's a lot of daylight to blank out below the running plate, the motion bracket carrying the expansion links will have to be a little further forward on a final mounting in order to make the valve gear look right, and there's a problem with the cylinders/slidebars/leading crankpins at present. If I cannot relieve material from the rear of the slidebars the cylinders will have to be mounted further apart than scale in order to obtain running clearances. The B1 motion was a fairly easy fit on the driving crankpin. I soldered a short stub of brass tube into the B1 big end eye to both bush and space out the con-rod, soldered a crankpin spacing washer behind the eye in the return crank and reamed that out to take the crankpin screw from the O4, and then tightened the screw in to retain the con-rod and to both retain and set the angle of the return crank on the flat end of the O4 crankpin.

And here are the main ingredients for an O4/8, thanks to another butchered B1 body:

[will5210]

That looks excellent! Probably my favorite Thompson loco

[davidwest]

Genius Graeme!

[coachmann]

Tantalising! I look forward to seeing your 04/8. I am considering an 04/7 but need a scale drawing to show the boiler diameter and smokebox lengthbefore rolling one.

Larry

[45609]

Larry,

Have a look at my posting on RMweb from a few minutes ago. The Isinglass drawing says the boiler diameter on the O4/7 is 5ft 9 7/8 inches. Various lengths are also listed.

Graeme,

Fantastic looking conversions. Your ingenuity never ceases to amaze me.

Cheers....Morgan

[Atlantic 3279]

Thanks Gents. Exploiting a chance to start late at work this morning, I had an hour working on the O1. Having filed as much as I dare off the rear of the slidebars, packed each cylinder out with a 0.5mm "plate" of plastikard (almost as Thompson did on the real thing I believe) AND slipped two split Peco fibre washers per side over the leading coupled axle (splitting and twisting them saved pulling a wheel off at risk to quartering and secure fixing) I do now appear to have some running clearance. I'll test run later. Countersunk crankpin screws on the leading two couped wheelsets would be nicer, but Bachmann don't offer such luxuries and I couldn't be bothered either.
Also shuffled the expansion link bracket forwards about 2.5mm. The link rocks through a rather more "balanced about the vertical" angle now! The eccentric rod probably ought to be shorter and the radius rod longer, but I'm going for minimum interference.

[coachmann]

Thanks Morgan, Isinglas drawing No. 489 ordered this afternoon for the 04/7.

Larry

[Atlantic 3279]

Running trials including 2 foot radius curves were passed with ease despite the now restricted sideplay on the leading coupled axle.
After some thinking, measuring and sketching I've now made and fitted a fill-in section from the loco mainframes above the first two coupled wheelsets, and the top of this incorporates two broad shallow transvers slots to properly accommodate and secure my stretchers for the cylinders and motion bracket. Hitherto, these were simply screwed somewhat crudely to the base of the boiler barrel - but that allowed me to work out what could go where.

Underside shaped to fit O4 motion bracket slot and screw hole:

Stretchers, cylinders and motion screwed in place.

The O1 is now largely complete, save for fill-in frames above the pony truck (which may be moved backwards slightly to its scale position first) and some new rear sandboxes below the cab.

Tomorrow I may get the main chunks of the O4/8 body put together as a trial / demo before further filling, smoothing, primer and detailing.

[mick b]

Very impressive

[Atlantic 3279]

Although I'm about to adjourn to concentrate on well-earned beer (after a long cycling session in heat and unfavourable wind today) thanks to some work done this evening I can present the promised first views of the O4/8, albeit body-only and dry-run.
I discovered that the B1 cab with its extended lower sidesheets needs some careful filing of material from its lower inside faces before it becomes a very snug fit over the raised cab floor casting of the O4 running plate. 2 -3mm of splasher has to be let in to the lower front corner of the longer B1 cab.

And here's a quick look at the almost fully-stripped O4 running plate, save for control rods for the front sandboxes. Once unscrewed, Boiler+saddle+cab+reversing rod come off, with careful easing and levering, all in one piece. Cab floor fittings can then be unplugged (or more likely snapped off, as the pins are well glued), and rear handrail too. In this picture my O4/8 saddle is already screwed in place.